car rental secondary coverage is enough?

Question

I rented car by Amex and it gives you car insurance. But this has only secondary coverage:

This benefit provides secondary coverage and does not cover liability, damages to vehicles other than those rented by the Card Member, and injuries to people in other vehicles.

But here is written:

If you don’t have personal auto insurance or if you’re renting a car in a country where your personal auto insurance isn’t in effect, then any card that offers secondary coverage becomes primary, so it should theoretically cover the entire cost of the damage.

So, I don't have personal auto insurance, doesn't it mean I don't need to buy additional primary coverage (from Amex), because it's already covered?

I just want to understand does it makes sense to buy Amex primary insurance if I already have it?

Answer 1

That Amex cover may become 'primary' if you have no other insurance, but it still won't cover

liability, damages to vehicles other than those rented by the Card Member, and injuries to people in other vehicles

It'll only cover damage to the car you're renting, lost revenue to the rental company, some medical/accidental death benefit to you and/or your passengers, and some loss/damage of you/your passengers personal property.

The Amex being 'primary' means that you don't have to report any incidents to another insurer first, and that Amex will cover the full amount of whatever is covered (up to whatever limits might be in place).
If you had other insurance, then the Amex would be secondary, and you would have to report to and claim from that other insurance before Amex would step in to pick up any leftovers (but they still wouldn't cover anything in the excluded list above).

**Some content shamelessly plagiarized from HartCO's comments.

Answer 2

This article suggests there is an Amex with a liability benefit:

However, one thing to note is that both primary and secondary coverage only insure damage to the rental vehicle and are not all-inclusive. Things such as personal injury, personal liability and damage to other vehicles and personal property are not covered under either car rental benefit. As per various sources (as well as agents at the car rental desk), apparently the only card that offers liability coverage on a rental by default is the American Express Centurion (Black) Card. Even American Express’ optional Premium Car Rental Protection doesn’t cover liability.